Introduction Excluding dural arteriovenous fistulas of the transverse-sigmoid sinus junction, posterior fossa dural arteriovenous fistulas (dAVF) are rare and dangerous cerebrovascular lesions to treat. They demonstrate a high risk of hemorrhage and develop in vasculature which supply several eloquent structures. Posterior fossa dAVFs frequently exhibit cortical or subarachnoid venous drainage and are located in technically challenging locations. Here, we review our experience with the management of these complex vascular lesions.

Methods A single multi-center health system retrospective chart review identified all patients from January 2015 to December 2022 who presented with posterior fossa dAVFs that did not drain to the transverse-sigmoid junction. Clinical data, structural and hemodynamic characteristics of the dAVF, rate of favorable clinical outcomes defined as a modified Rankin Scale (mRS) of 0-2, and technical parameters including anatomic or surgical approach, embolic agent used, complications, and embolization success were reviewed.

Results Out of 208 patients treated for dAVF, 29 patients (13.94%) presented with posterior fossa dAVF that did not drain to the transverse-sigmoid junction. 18/29 (62.07%) of dAVFs were located on the tentorium while 11/29 (37.93%) of dAVFs were located on the skull base. Patients mostly presented with benign symptoms such as posterior headache, but 2 patients (6.9%) presented due to rupture of their dAVF with associated hemorrhage. 67.74% of the dAVFs demonstrated cortical or subarachnoid venous drainage: 11 Cognard type III, 9 Cognard type IV, and one Cognard type V. 17 patients received endovascular embolization (58.62%). 68% of embolizations were transarterial alone, 16% were transvenous alone, and 16% were performed with a combined transarterial and transvenous approach. Ethylene vinyl alcohol copolymer (EVOH) was the most common embolic agent, utilized in 72% of embolizations. Technical success was achieved in 23/25 (92%) embolizations, with both failures occurring due to vessel tortuosity preventing transarterial navigation. 11 patients (37.93%) patients received at least one open surgery for ligation of their fistula: 6 patients received a suboccipital craniotomy, 4 received a middle fossa transtentorial craniotomy, 2 received a retrosigmoid craniotomy, and 1 patient received a decompressive hemicraniectomy due to rupture of their dAVF. On subsequent angiography, 4 patients (13.8%) demonstrated recurrence of a posterior fossa dAVF after surgical obliteration with a change in venous drainage pattern from the venous sinuses to a cortical venous drainage consistent with Cognard type III. This required further open or endovascular intervention with eventual obliteration of the recurrent fistula. On long-term clinical follow-up, 75.86% of patients demonstrated favorable clinical outcomes.

Conclusion Surgical intervention was often indicated for posterior fossa dAVFs and a small percentage of fistulas recurred with pathological venous drainage patterns. Careful patient selection and preoperative planning are necessary to ensure favorable clinical outcomes.

Disclosures A. Devarajan: None. D. Goldman: None. A. Schupper: None. B. Giovanni: None. R. De Leacy: None. A. Berenstein: None. J. Fifi: None. T. Shigematsu: None.